Fusion constructs containing active sections on TNF ligands

ABSTRACT

Disclosed is a recombinant fusion protein containing an amino-acid sequence which comprises: (a) the Fc section or part of an Fc section of an immunoglobulin as component (A) or a functional variant of component (A); (b) the extracellular part of a TNF ligand or a partial sequence of the extracellular part of a TNF ligand as component (B) or a functional variant of component (B); and optionally (c) a transition area between component (A) and component (B), containing a linker.

This application claims the benefit of foreign priority from DE 10205368.5 filed Feb. 10, 2002 and DE 10205583.1 filed Feb. 11, 2002.

The prior art discloses a large number of receptors which belong to the TNF receptor class and which in each case interact with at least one TNF ligand as the physiological ligand. The receptors of the TNF receptor family are type I membrane proteins (Nagata et al., Science, 267: 1449, 1995). An example of a well-investigated TNF receptor/TNF ligand system is the Fas receptor (Fas, FasR, CD95), which interacts with the natural ligand FasL and, in this way, induces an intracellular signal. The importance of the FasL/FasR system for cell-specific cell death has, in particular, been thoroughly investigated. The rat Fas ligand (Suda et al., Cell 75: 1169, 1993; Lynch et al., Immunity 1:131, 1994) and the human form of the ligand (Takahashi et al., International Immunology 6: 1567, 1994) have been cloned at the cDNA level. As a member of the TNF ligand family, FasL belongs to the category of type II membrane proteins, i.e. FasL possesses an extracellular carboxyterminal domain and an intracellular aminoterminal domain. The proteins TNFa (tumor necrosis factor a) and TNFβ (tumor necrosis factor β, Eck et al., Journal Biological Chemistry 264: 17595, 1989), for example, also belong to the TNF ligand family. Each of the TNF ligands binds to its physiological TNF receptor. Other examples of these ligands from the prior art are OX40L (binds to OX40R), CD27L (binds to CD27R), CD30L (binds to CD30R), RANKL (binds to RANK-R), CD40L (binds to CD40R), TRAIL (binds to TRAIL-R1, R2, R3 or R4) and TWEAK (binds to Fn14).

However, the native forms of the ligands belonging to the type II membrane protein family are not suitable as such for medical use. As membrane proteins, they cannot be administered as such, either, because of the hydrophobic transmembrane domain, in particular.

Attempts were therefore made, in the prior art, to make available TNF ligand fragments which might still be able to exhibit the physiological effect but which do not possess the intracellular segments or the transmembrane domain. For example, in-vitro and in-vivo experiments have been carried out using FasL fragments which only exhibit regions of the FasL domains which are disposed extracellularly in the native state (sFasL, i.e. soluble FasL). However, these protein fragments were only able to fulfil the physiological function of the ligands inadequately, particularly in the case of FasL, with the soluble extracellular FasL domain even sometimes being observed to exhibit unwanted effects which were the inverse of those of the FasL transmembrane protein, which is evidently present in active form as a trimer under physiological conditions.

The object of the present invention is therefore to make available sequences which not only imitate and reproduce the physiological effects of TNF ligands, for example FasL, but are also soluble and are therefore suitable for being used as pharmaceuticals, in particular for producing medicaments as well.

The invention makes available fusion constructs, i.e. both nucleotide sequences and the protein sequences which are derived from the nucleotide sequences, which also make it possible, in particular, to abolish the phenotype of genetically determined diseases, with it being possible to use specific therapeutic methods according to the invention for this purpose. Fusion constructs of the type according to the invention typically exhibit a structure as depicted in FIG. 1. A construct according to the invention contains at least two components (A) and (B), namely a segment which is located N-terminally in the construct and which contains the sequence of the constant region of an immunoglobulin, or a fragment or a variant, for example a deletion mutant, substitution mutant or insertion mutant, (component A) and a sequence or part sequence of a ligand of the TNF ligand family (type II, component (B)), which is located more C-terminally in the fusion construct. According to the invention, the segment of the immunoglobulin (Ig), which is located N-terminally in the fusion construct, that is component (A), does not exhibit the variable region which is characteristic of immunoglobulins and which is responsible for antigen recognition but, instead, only exhibits domains, or segments of domains, of the immunoglobulin constant region, for example the domain(s) CH₁, CH₂ and/or CH₃. It is consequently possible, according to the invention, for segments of these CH domains, that is, for example, the domain CH₁ and the domain CH₃, to be linked to each other as component (A), in connection with which component (A) should not, according to the invention, lose its ability to bind to physiological Fc receptors during a treatment in utero. In the case of a postnatal treatment, the situation appears to be such that, where appropriate, it would be advantageous if the constructs according to the invention did not bind to Fc receptors. It can consequently be preferable, in the case of postnatal therapy, for component (A) to specifically no longer possess the property of binding functionally to Fc receptors. Such a loss of function can be achieved, for example, by means of inserting, deleting or replacing functional Fc sequences.

The immunoglobulin sequence which is derived from the Fc region and which is present as component (A) in the fusion construct according to the invention may be able to dimerize with another fusion construct or to be present as a monomer. Preference is given to component (A) being capable of dimerizing with a fusion construct according to the invention, which is preferably identical, or else, alternatively, with another fusion construct according to the invention, for example a fusion construct containing another component (B). The dimerization can take place by way of a disulfide bridge using the hinge region which, in a native state, is located between domain CH₁ and domain CH₂, or else also by way of an artificially introduced sequence (or else, for example, substitution/insertion of a cysteine) which is able to dimerize covalently (disulfide bridge) or noncovalently (for example leucine zipper or other sequence segments which are suitable for dimerizing). However, the fusion construct according to the invention can also be present as a single-chain antibody.

In a preferred embodiment, the constant region of the antibody in the fusion protein will be of human origin, for example originating from the antibody GI2765420, and belong to the immunoglobulin family derived from the IgG class of immunoglobulins, in particular from classes IgG1, IgG2, IgG3 or IgG4, preferably from the class IgG2 or IgG4. It is also alternatively possible to use constant regions of immunoglobulins belonging to the IgG class from other mammals, in particular from rodents or primates; however, it is also possible, according to the invention, to use constant regions of the immunoglobulin classes IgD, IgM, IgA or IgE. Typically, the antibody fragments which are present in the construct according to the invention will comprise the Fc domain CH₃, or parts thereof, and at least one part segment of the Fc domain CH₂. Alternatively, it is also possible to conceive of fusion constructs according to the invention which contain, as component (A), the CH₃ domain and the hinge region, for the dimerization.

However, it is also possible to use derivatives of the immunoglobulin sequences which are found in the native state, in particular those variants which contain at least one replacement, deletion and/or insertion (combined here under the term “variant”). Typically, such variants possess at least 90%, preferably at least 95%, and very particularly preferably at least 98%, sequence identity with the native sequence. Variants which are particularly preferred in this connection are replacement variants which typically contain less than 10, preferably less than 5, and very particularly preferably less than 3, replacements as compared with the respective native sequence. Attention is drawn to the following replacement possibilities as being preferred: Trp with Met, Val, Leu, Ile, Phe, His or Tyr, or vice versa; Ala with Ser, Thr, Gly, Val, Ile or Leu, or vice versa; Glu with Gln, Asp or Asn, or vice versa; Asp with Glu, Gln or Asn, or vice versa; Arg with Lys, or vice versa; Ser with Thr, Ala, Val or Cys, or vice versa; Tyr with His, Phe or Trp, or vice versa; Gly or Pro with one of the other 19 native amino acids, or vice versa.

Very particular preference is given, for the treatment in utero, to those modifications of the abovementioned nature where the binding to membrane-located Fc receptors is at least not impaired but is, where appropriate, even optimized. However, when using constructs according to the invention for postnatal therapy, preference is given to minimizing or even abolishing the ability to bind to Fc receptors. Since fusion constructs according to the invention must contain, as component (A), sequences which have to retain the ability to bind to the respective physiological receptors for the constant segment of immunoglobulins, the amino acids at, in particular, positions 230 to 240, more preferably at positions 234 to 237, of domain CH₂ in the antibody fragment used as component (A) will consequently not be altered or only be provided with the sequence variations which leave the binding behavior with respect to Fc receptors, for example, unimpaired. On the other hand, preference is particularly given to replacements or deletions, as compared with the native sequence of immunoglobulin constant regions, at those positions which result in glycosylation sites being eliminated or inserted, disulfide bridges being inserted or eliminated, impair the stability or solubility, or improve passage through the cell membrane following binding following Fc receptors. Preference is given, in particular, to those variants which do not exhibit any structural changes, or only negligible structural changes, as compared with the three-dimensional folding of the native sequence. Such structural identity (and thus functional homology) can be determined by means of plotting appropriate spectra, for example a circular dichroism spectrum of the native sequence or of the given variant. The form of the spectrum, particularly in a measurement range between 190 and 240 nm wavelength, can always be used to establish structural identity. In this connection, the reader is referred, in particular, to the relevant literature of the manufacturers of instruments for measuring CD (e.g. Jasco, Japan).

C-terminally of the immunoglobulin fragment, a fusion construct according to the invention typically, but not necessarily, contains a transition region between components (A) and (B), which transition region can in turn contain a linker sequence, with this linker sequence preferably being a peptide sequence. This peptide sequence can have a length from between 1 and up to 70 amino acids, where appropriate even more amino acids, preferably from 10 to 50 amino acids, and particularly preferably between 12 and 30 amino acids. Examples of particularly strongly preferred transition sequences are depicted in FIGS. 1 b to 1 j (correspondingly labelled in these figures). The linker region of the transition sequence can be flanked by further short peptide sequences which can, for example, correspond to DNA restriction cleavage sites. Any restriction cleavage sites with which the skilled person is familiar from molecular biology can be used in this connection. Suitable linker sequences are preferably artificial sequences which contain a high number of proline residues (for example at every second position in the linker region) and, in addition to that, preferably have an overall hydrophilic character. A linker sequence which consists of at least 30% of proline residues is preferred. The hydrophilic character can preferably be achieved by means of at least one amino acid having a positive charge, for example lysine or arginine, or negative charge, for example aspartate or glutamate. Overall, the linker region therefore also preferably contains a high number of glycine and/or proline residues in order to confer on the linker region the requisite flexibility and/or rigidity.

However, native sequences, for example those fragments of ligands belonging to the TNF ligand family which are disposed extracellularly, but immediately act, i.e. in front of, the cell membrane, are also suitable for use as linkers, where appropriate after replacement, deletion or insertion of the native segments as well. These fragments are preferably the 50 AA which follow extracellularly after the transmembrane region or else subfragments of these first 50 AA. However, preference is given to these segments having at least 85% sequence identity with the corresponding natural human sequences, with very particular preference being given to at least 95% sequence identity and particular preference being given to at least 99% sequence identity in order to limit the immunogenicity of these linker regions in the fusion protein according to the invention and not elicit any intrinsic humoral defense reaction. Within the context of the present invention, the linker region should preferably not possess any immunogenicity.

However, as an alternative to peptide sequences which are linked to the antibody fragment and the TNF ligand, or a fragment of such a TNF ligand, by way of amide-like bonds, it is also possible to use compounds which are of a nonpeptide or pseudopeptide nature or are based on noncovalent bonds. Examples which may be mentioned in this connection are, in particular, N-hydroxysuccinimide esters and heterobifunctional linkers, such as N-succinimidyl-3-(2-pyridyldi-thio)propionate (SPDP) or similar crosslinkers.

In a fusion protein according to the invention, the transition region is typically followed carboxy-terminally by a sequence of a member of the TNF ligand family, or a fragment or a variant thereof, as component (B) in a fusion construct according to the invention. Within the context of the present invention, preference is given to fragments which contain, in particular, the part of the extracellular segment of a member of the TNF ligand family which has the outermost carboxyterminal location. The following TNF ligand family members, or variants or fragments thereof, are particularly preferred within the context of the present invention: FasL, TNF α/βTRAIL, Tweak, LIGHT, CD40L, RANKL, CD30L, OX40L, CD27L, EDA1, BAFF and EDA2. The reader is referred to the corresponding entries in the SwissProt database with regard to the native sequences of the extracellular segments of the abovementioned proteins.

Preference is given, with regard to FasL, to fragments of amino acids 100 to 281 of the native sequence or fragments which are more truncated at the N terminus (e.g. AA 101 or 102 to 281), in particular 120 to 281 and very particularly 139 to 281, or fragments which are even more truncated at the N terminus, as component (B), or fragments which are even more truncated at the N terminus, while preference is given, with regard to EDA1, to fragments of amino acids 140 to 391, or fragments which are more truncated at the N terminus (e.g. 157, 160, 181 or 182 to 391), in particular 200 to 391, very particularly 245 to 391, or fragments which are even more truncated at the N terminus (e.g. 246 to 391), with regard to EDA2, to amino acids 180 to 389 or fragments which are more truncated at the N terminus (e.g. 181 or 182 to 389), or also preferably 200 to 389 and even more preferably 245 to 389 or fragments which are even more truncated at the N terminus, with regard to TNFa, to amino acids 50 to 228 or fragments which are more truncated at the N terminus (e.g. AA 51 or 52 to 228), more preferably 70 to 228, and most preferably 80 to 228, or fragments which are even more truncated at the N terminus, with. regard to CD40L, to fragments of the segments 80 to 261 or fragments which are more truncated at the N terminus (e.g. 81 or 82 to 261), more preferably 100 to 261 and most preferably 116 to 261 or fragments which are more truncated at the N terminus (or fragments which are even more truncated at the N terminus), with regard to TRAIL, to amino acids 70 to 281 or fragments which are more truncated at the N terminus (e.g. AA 71 or 72 to 281), more preferably 80 to 281, and most preferably 95 to 281, or fragments which are even more truncated at the N terminus, with regard to BAFF, to amino acids 100 to 285 or fragments which are more truncated at the N terminus (e.g. AA 101 or 102 to 285), more preferably 120 to 285, and most preferably 137 to 285, or fragments which are even more truncated at the N terminus, and with regard to APRIL, to amino acids 80 to 233 or fragments which are more truncated at the N terminus (e.g. 81 or 82 to 233), more preferably 90 to 233, and most preferably 98 to 233, or fragments which are even more truncated at the N terminus. However, all the sequence segments which are located between the ranges which are in each case mentioned above as being preferred can also be used in the N-terminal region of the sequences which are present as component (B) in the fusion protein according to the invention, with a fusion protein according to the invention typically terminating C-terminally with the native C-terminal end of the TNF ligand. However, it is also possible, where appropriate, for at least one amino acid, typically from 2 to 10 amino acids, in rare cases even more than 10 amino acids, to be deleted in the C-terminal region of the extracellular TNF ligand fragment which is used as component (B) in the fusion protein according to the invention.

The TNF ligand which is present in the fusion protein according to the invention can also contain at least one replacement, deletion and/or insertion, as compared with the native sequence, for the purpose of expressing desired biological effects such as solubility, stability or altered immunogenicity. As an alternative to the native TNF ligand sequence, it is also possible, according to the invention, to use, as component (B) in the fusion protein according to the invention, a variant which typically exhibits at least 75%, preferably 85%, and particularly preferably at least 95%, sequence identity with the native sequence and which has the same biological effect and is consequently functionally homologous in this respect. Such structural identity (and thus functional homology) can be determined by means of plotting appropriate spectra, for example a circular dichroism spectrum of the native sequence or of the given variant. The form of the spectrum, particularly in a measurement range between 190 and 240 nm wavelength, can always be used to establish structural identity. In this connection, the reader is referred, in particular, to the relevant literature of the manufacturers of instruments for measuring CD (e.g. Jasco, Japan).

Variants which are particularly preferred in this connection are replacement variants which typically contain less than 10, preferably less than 5, and very particularly preferably less than 3, replacements as compared with the respective native sequence. Attention is drawn to the following replacement possibilities as being preferred: Trp with Met, Val, Leu, Ile, Phe, His or Tyr, or vice versa; Ala with Ser, Thr, Gly, Val, Ile or Leu, or vice versa; Glu with Gln, Asp or Asn, or vice versa; Asp with Glu, Gln or Asn, or vice versa; Arg with Lys, or vice versa; Ser with Thr, Ala, Val or Cys, or vice versa; Tyr with His, Phe or Trp, or vice versa; Gly or Pro with one of the other 19 native amino acids, or vice versa.

However, alternatively, and finally, it is also possible to use, as component (B), a substance which imitates the effects of physiological ligands, for example an organic molecule which has an agonistic effect on the corresponding TNF family receptor or an antibody which can bind agonistically to a TNF receptor and, after interaction with the receptor, induce the biological function of the physiological TNF ligand. As an example, mention may be made of the function of FasL, which function can also be achieved by an antibody, such as APO-1, as component (B), in a fusion construct according to the invention. Polypeptides which are able to introduce the physiological effect of TNF ligands can be identified, for example, by means of appropriate phage display methods (see U.S. Pat. No. 5,223,409, the entire teaching of which is hereby incorporated into the present disclosure by reference).

The invention also relates to a method for reversing genetically determined diseases or to a use of a fusion protein according to the invention for producing and formulating a pharmaceutical for a corresponding therapeutic method according to the invention. This method according to the invention can be used in connection with all Placentalia, that is vertebrates possessing a placenta, in particular in human and veterinary medicine. Following diagnosis of a genetically determined disease in an embryo, for example by means of chorion biopsy or amniocentesis, or when a genetically determined disease is suspected in an embryo on the basis of the genetic disposition of relations, in particular father and/or mother, the method according to the invention is suitable for already treating the embryo prophylactically and reversing its hereditary phenotype. The treatment is effected using a fusion protein according to the invention, as disclosed above, where appropriate in a corresponding formulation, and is ideally administered to the mother, or the mother animal, at the earliest possible time in the pregnancy. Such a fusion protein according to the invention is advantageously administered parenterally, preferably intravenously or intraarterially.

After a pharmaceutical has been administered, a fusion protein which is in accordance with the invention and which is of the previously described type binds, according to the invention, by way of its Fc moiety, as component (A), to the Fc receptors in the placenta and in this way, after having been internalized, reaches the embryo, typically by way of the placental vessels which connect the embryo to maternal blood circulation.

The dose depends on the genetic disease itself and on the time of the administration (that is on the developmental stage of the embryo), in connection with which the treatment should advantageously start at the earliest possible time in the development of the embryo. These Fc:ligand constructs according to the invention, e.g. Fc:EDA1 or Fc:EDA2, are administered at least once, more preferably regularly during the first, second and/or third month of the pregnancy, very particularly preferably, for example, on every second day for a period of at least 14 days in the case of a human embryo, where appropriate, however, at longer intervals as well depending on the dose which is chosen.

In principle, however, the dose of a fusion construct according to the invention depends on the method of treatment. In the case of treatment by the method according to the invention, that is during embryonic development, typical doses of the administered construct of less than one tenth, preferably less than one hundredth, and even more preferably less than one thousandth, of the native concentration of the TNF ligand in the neonate are recommended. When the neonate or the infant is being treated with a fusion protein according to the invention, the doses will be at least 1/100, more preferably at least 1/10 (always based on the TNF ligand activity) of the serum concentration which is typical for a healthy patient of the same age.

Very particular preference is given to a method according to the invention, or to the use of a fusion protein according to the invention for formulation as a pharmaceutical in such a method, when a fusion construct according to the invention is administered which carries an Fc moiety at the N terminus of the fusion construct and, as component (B) at the C terminus, a segment of the TNF ligand EDA1 or EDA2, in particular EDA1 or EDA2 of human origin, in particular an extracellular segment of these proteins which extends from at least amino acid 200 to amino acid 391 (EDA1) or up to amino acid 389 (EDA2), very particularly preferably from amino acid 245 to 391 (EDA1) and from amino acid 245 to 389 (EDA2). Those fusion constructs according to the invention as are depicted in FIGS. 1 d and 1 e are even more preferred for a method according to the invention or for a corresponding use.

In veterinary medicine, these fusion constructs according to the invention can be used to reverse the phenotype of the progeny of tabby mice by means of treating the mice, in accordance with the method, during pregnancy. Correspondingly, a method according to the invention, or the use of fusion proteins according to the invention for producing pharmaceuticals which are suitable for the method, can also be employed for therapeutic treatment of the analogous human disease, that is an hereditary disease which is based on the same genetic defect, namely X-coupled hypohydrotic ectodermal dysplasia (XLHED, Christ-Siemens-Touraine Syndrome), the most frequent form of ectodermal dysplasia. XLHED is due to a defect in the ED1 gene, with this defect corresponding, in human medicine, to the following clinical disease picture: hyposomia, varying degrees of dementia, saddle nose, anhidrosis, missing teeth or abnormal development of the teeth, hypertrichosis or alopecia, or dysfunction or lack of eccrine sweat glands, for which reason the affected patients are extremely susceptible to hyperthermia. Apart from XLHED, other ectodermal dysplasias, which are based on other hereditary causes, can also be treated in the manner according to the invention, either during embryonic development or else conventionally, by means of administration to the neonate or the infant.

The present invention consequently also relates to the use of fusion constructs according to the invention for treating genetically determined diseases in humans or animals, in particular by means of a method in accordance with the invention, as described above, or for producing a pharmaceutical. Fusion constructs according to the invention, in particular constructs which contain segments of the TNF ligand EDA1 or EDA2, for example the fusion constructs in accordance with FIG. 1 d and FIG. 1 e, are particularly suitable, in a general manner, for treating (or for producing a pharmaceutical for treating) genetically determined skin anomalies, in particular anomalies of the skin structure or else anomalies of ectodermal structures such as anomalies of the hair, of the teeth or of the glands (anhidroses or dyshidroses of varying genesis). An example which may be mentioned is the use of fusion proteins according to the invention in the cosmetic field, for example for treating alopecia, either acquired (for example in the form of alopecia areata, alopecia atrophicans, alopecia seborrhoeica or alopecia praematura) or congenital (especially as the syndrome of anhidrosis hypotrichotica) or hirsutism. However, fusion constructs according to the invention can also quite generally be used for treating, or for producing a pharmaceutical for treating, all forms of ectodermal dysplasia. For this reason, fusion constructs according to the invention, in particular those involving EDA1 or EDA2, are particularly suitable for treating, or for producing a pharmaceutical for treating, stimulation of hair growth or inhibition of hair growth, for treating disturbances in the growth of the teeth, or else for treating disturbances in gland function, including that of the sweat glands and/or sebaceous glands, or are suitable for promoting hair follicle formation or wound healing, in particular for promoting wound healing in patients for the purpose of ensuring appropriate growth of hair on the affected area of the skin. These fusion constructs can be used in a conventional manner, i.e. by preferably administering them to the patient postnatally, in human therapy very particularly preferably within the first year of life, even more preferably within the first 6 months of life, even more preferably within the first 2 months of life, even more preferably within the first 2 weeks of life and even more preferably within the first 3 days after birth, or else by means of the method described in accordance with the invention, i.e. by administering them to the pregnant mother or mother animal, e.g. by means of injection in utero. The fusion constructs according to the invention can consequently also be used for treating the abovementioned syndromes, genetic diseases or disturbances during embryonic development, by administering them to the mother or the mother animal.

When using constructs according to the invention for producing a pharmaceutical for treating, or treating, in particular, alopecia or, in particular, for promoting wound healing, for example following skin burns or inflammatory skin diseases, e.g. when treating neurodermitic or atopically affected areas of the skin, in particular of the scalp, it is also suitable to administer these constructs, where appropriate while using other auxiliary substances, carrier substances or additives, and also other active compounds where appropriate (e.g. when treating alopecia: Relaxin, substances having an antiandrogenic effect, e.g. finasteride, SKL-105657, oestrogen, cyproterone acetate, spironolactor, flutamide, minoxidil and/or RU58841) to adults, for example by means of intravenous or intraarterial or subcutaneous administration, following appropriate processing (formulation), or else orally or as a cream, lotion or ointment for topical use.

Another possible area of employment for constructs according to the invention is their use in producing skin tissue ex vivo. For example, items according to the invention, for example in the form of the proteins, the nucleic acids or the expression vectors, can be used in order to (re)generate the natural functionality of the skin of patients suffering from skin diseases (for example diabetic ulcers) or burns, with the formation of eccrine glands, hair follicles and hair. In this connection, items according to the invention are added to cells or tissues in vitro. For example, items according to the invention can be used in the traditional method of skin grafting; that is, for example, autologous, healthy skin tissue from the patient, allogenic skin tissue from deceased persons or donors, or animal tissue, can be stimulated, before being transplanted and by treatment with fusion constructs according to the invention, to form hair follicles or eccrine glands, for example within the context of a pretreatment or within the context of extracorporeal culture. However, it is also possible to isolate multipotent precursor cells from healthy skin tissue (or other tissue) from the patient himself. These cells are formed into skin tissue by adding appropriate differentiation factors. These multipotent precursor cells can, by means of appropriate transfections, be transfected with sequences or expression vectors according to the invention, or else fusion constructs can be added to them during the formation of skin tissue. In this way, it is possible to use items according to the invention in what is termed “tissue engineering” (tissue culture) before the cultured tissue is retransplanted into the patient. For this, the tissue to be transplanted (precursor cell, stem cell or tissue cell) (in particular keratinocytes of the epidermis) or embryonic stem cell (autologous or allogenic) is in principle first of all isolated and then cultured in an open system on a matrix (natural, synthetic or xenogenic) or a biodegradable framework, with the cells being supplied adequately with added nutrients, oxygen, growth factors and constructs according to the invention and with harmful metabolites being eliminated. The present invention consequently also relates to an in-vitro method for culturing skin tissue which exhibits eccrine glands and natural hair growth.

In principle, a large number of genetic diseases, in particular hereditary diseases which are due to faulty expression of members of the TNF ligand family, can be treated in the manner in accordance with the invention. An example of another genetic disease which using a fusion construct according to the invention which contains an Fc moiety and a biologically active segment of CD40L as component (B), is immunodeficiency associated with hyperIgM (HIGM1), which is X-chromosomally linked and is an immunoglobulin isotype switching defect which is characterized by an elevated concentration of serum IgM and reduced concentrations of other Ig isotypes. This disease is due to a defect in the TNFSF5 gene. The syndrome of HIGM1 which this causes is due to defective expression of the CD40 ligand, which results in a defect in immunoglobulin isotype switching. A genetic defect of this nature affects, in particular, male patients in their early years (within the first 5 years of life), with these patients being especially susceptible to opportunistic infections and therefore falling victim to an unfavorable survival prognosis. By using a fusion construct according to the invention which contains an active segment of the extracellular CD40L domain as component (B), it is possible, for example by employing a method according to the invention for treatment during embryonic development, to achieve partial reconstitution of the precursor T cells which are capable of expressing the functional CD40 ligands, with this resulting in the chemical symptoms of this genetic disturbance being relieved.

Another part of the subject-matter of the present invention is directed towards the recombinant DNA constructs on which the fusion proteins according to the invention are based. Within the context of the present invention, DNA and protein constructs are dealt with jointly under the term “fusion constructs”. Thus, a nucleotide construct according to the invention can, for example, encode the CH2 and CH3 domains of IgG, as component (A), and, for example, CD40L or EDA1 or BAFF or FasL, where appropriate linked by a transition region containing a linker. Accordingly, the underlying recombinant nucleotide sequences according to the invention encode all the protein fusion constructs according to the invention which have previously been disclosed. Particular preference is given to the nucleotide sequences of the fusion constructs disclosed in FIG. 1. The nucleotide constructs according to the invention can be obtained, as cDNA, genomic DNA or in synthetic form, using cloning methods or by way of chemical synthesis, with a large number of methods from the prior art being suitable. For example, with regard to the sequences of the immunoglobulin Fc moiety domain which can appear in a nucleotide construct according to the invention, the reader is referred, for example, to the publication “Sequences of Proteins of Immunologic Interest”, 1^(st) Edition, Kabat et al., US Department of Health and Human Services, 1991”, with the entire content of this publication hereby being incorporated into the present disclosure by reference.

The sequences which are contained in a nucleotide construct according to the invention will typically be present in segments which are assembled by means of restriction and ligation. A nucleotide sequence according to the invention will typically contain expression control sequences, including promoters, ribosome binding sites, polyadylation sites and/or transcription termination sites, and, where appropriate, enhancers, which are operably linked to the nucleotide sequence according to the invention for a fusion protein according to the invention. A fusion protein according to the invention can be expressed by transfecting DNA segments containing such regulatory elements, for example on plasmid vectors, into bacterial cells, yeast cells, plant cells, insect cells and, preferably, mammalian cells, for example using the calcium phosphate method, electroporation or similar techniques. For achieving expression in eukaryotic cells, use is made of the promoter and, where appropriate, the enhancer sequence of, for example, immunoglobulin genes, SV40, retroviruses, cytomegalovirus, elongation factor Iα, etc. Preferred host cell lines include CHO cells, COS cells, Hela cells, NIH3T3 cells and various myeloma or hybridoma cell lines, including P2/0 and NS/0. The present invention relates to such a DNA sequence according to the invention which encodes a recombinant fusion protein according to the invention, to expression vectors which contain such a DNA sequence according to the invention and to host cells which are transfected with such an expression vector according to the invention.

All the abovementioned indications can also be treated with the DNA constructs, expression vectors or host cells according to the invention. In particular, the reader is referred, in this connection, to the corresponding therapeutic methods used in in-vivo or ex-vivo gene therapy (for example transfection of bone marrow cells). In this connection, very particular preference is given to gene therapy methods used in the developing embryo, that is, for example, removal of embryonic cells, for example embryonic stem cells as well, with this being followed by ex-vivo transfection with material according to the invention, for example an expression vector according to the invention, for example a retroviral or adenoviral carrier, and reimplantation into the embryo. The DNA construct according to the invention is preferably located downstream of a regulable promoter.

The plasmid vector comprising a DNA construct according to the invention will generally contain a selectable marker, such as gpt, neo, hyg or DHFR, and an amp, tet, kan, etc. gene, for expression in E. coli. A large number of plasmid vectors which is suitable for expressing heterologous proteins is available in the prior art. A fusion protein according to the invention advantageously contains a N-terminal sequence, for example a hemagglutinin sequence and/or tag sequences and/or at least one further “LEADER” sequence at the amino terminus of the fusion protein, in order to facilitate secretion of the fusion proteins from the cell, in particular passage through the ER into the extracellular space or into the medium.

Methods for constructing nucleotide constructs according to the invention which encode protein constructs according to the invention, for their linking to expression control sequences and/or their insertion into plasmids, for transfection into cells and the selection and, if desired, gene amplification of the fusion protein-expressing cell line, can be carried out using methods which are known from genetic manipulation, including restriction enzyme digestion, ligation, oligonucleotide sequences and PCR reaction (Sambrook et al., Molecular Cloning: Laboratory Manual, 3^(rd) Edition, Cold Spring Harbor Laboratory Press, 2001), with the entire content of this publication hereby being incorporated by reference in this regard.

A transfected cell line which is expressing and secreting a fusion protein according to the invention is selected and can, where appropriate, be cultured in serum-free medium (hybridoma SFM), by being passed through a decreasing concentration of serum, and can finally be subcloned. A fusion protein according to the invention can be purified (from what is preferably serum-free medium) after having been secreted, with the expression cell line having been cultured. Standard methods for purifying proteins include filtration, precipitation, protein A affinity chromatography, gel filtration, ion exchange chromatography, electrophoretic methods or the like. Essentially pure fractions of the fusion protein, of at least 90 to 95% homogeneity and preferably of at least 98 to 99% or higher, homogeneity, are then preferably employed for the pharmaceutical use.

The production of a pharmaceutical which comprises the fusion protein according to the invention will typically include its formulation in a pharmaceutically acceptable carrier material. This carrier material will typically comprise aqueous carrier materials, with use being made of water for injection (WFI) or water buffered with phosphate, citrate or acetate, etc., and the pH being typically adjusted to 5.0 to 8.0, preferably 6.0 to 7.0. The pharmaceutically acceptable carrier will additionally and preferably contain salt constituents, e.g. sodium chloride or potassium chloride, or other components which make the solution isotonic. Furthermore, the carrier can contain additional components such as human serum albumin, polysorbate 80, sugars and amino acids. A composition according to the invention of this nature can be combined, in the form of an injection or as a kit, in an appropriately suitable combination with a pharmaceutically acceptable carrier material or a mediator, such as sterilized water or physiological sodium chloride solution, vegetable oils, mineral oils, higher alcohols, higher fatty acids and non-toxic organic solvents, and, where appropriate, be provided with further additives. Examples of further additives which are suitable are fillers (for example saccharides (lactose, sucrose, mannitol or sorbitol), calcium phosphate, cellulose or their derivatives), binders (for example starch, gelatine and polyvinylpyrrolidone), stabilizers, preservatives, antiadsorbents, surface-active substances, dyes, flavorings, emulsifiers, buffering agents, isotonic agents, antioxidants, analgesics or the like. Sodium alginate, polyethylene glycol and/or titanium dioxide are, for example, preferably worked into the formulations. Corresponding formulations of a pharmaceutical are disclosed in Remington (1980), to which the reader is referred in this regard.

The concentration of the fusion protein according to the invention in formulations of this nature can vary within a wide range of from 0.001 to 10 mg per ml, preferably in a range of from 0.5 to 5 mg/ml. The formulation is preferably injected into the patient or the pregnant mother parenterally, that is, for example, intravenously, intraarterially, subcutaneously or intramuscularly. Alternatively, when treatment is being carried out using a method according to the invention, it is also possible to introduce the formulation directly into the vascular system of the embryo placenta or inject it into the amniotic sac.

The present invention is clarified by means of the following figures:

FIG. 1 shows the nucleotide and amino acid sequences of Fc:ligand constructs which are in accordance with the invention and which are used in accordance with the invention.

In this connection, FIG. 1 a depicts, by way of example and diagrammatically, the sequence segments of particularly preferred Fc:ligand constructs according to the invention. A signal peptide is typically located in the N-terminal region of a fusion protein according to the invention, which is encoded by an underlying nucleotide sequence, with this signal peptide being followed by an IgG Fc segment (component (A)), which is in turn followed by an (optional) linker region and, more C-terminally, by an (optional) protease cleavage site sequence and, more C-terminally (and at the C terminus of a fusion construct according to the invention) by a sequence which typically constitutes a sequence of part of a member of the TNF ligand family (component (B)). This part sequence which serves as component (B) in turn typically includes the C-terminal moiety of the extracellular segment of a ligand from the TNF family.

Constituent FIGS. 1 b to 1 j show specific sequences of constructs according to the invention, with these constructs using different members of the TNF ligand family, namely FasL (FIGS. 1 b (SEQ ID NO: 2) and 1 c (SEQ ID NO: 4), with and without a protease cleavage site), EDA1 and EDA2 (FIGS. 1 d (SEQ ID NO: 6) and 1 e (SEQ ID NO: 8)), TNFa (FIG. 1 f (SEQ ID NO: 10)), CD40L (FIG. 1 g SEQ ID NO: 12)), TRAIL (FIG. 1 h (SEQ ID NO: 14)), BAFF (FIG. 1 j (SEQ ID NO: 16)) and APRIL (FIG. 1 i (SEQ ID NO: 18)). The constituent sequences of the abovementioned members of the TNF ligand family are all of human origin and in each case possess the C-terminally located extracellular sequence segments of the native ligands, up to the native C terminus. The Fc domain (component (A)), which is located N-terminally, is linked to the TNF ligand segment (component (B)), which is located C-terminally in the fusion protein, by way of a linker region containing the amino acids PQPQPKPQPKPEPE (SEQ ID NO: 19). In addition to this, the sequences of fusion constructs according to the invention as depicted in FIGS. 1 b, 1and 1 j contain a protease cleavage site, in each case having the sequence LEVLFQGP (SEQ ID NO: 20), such that the protease PreSCISSION (Amersham-Pharmacia) can cut the fusion constructs which are designed with such a protease cleavage site and thereby separate the immunoglobulin domain of the fusion construct from the TNF ligand segment. However, all sequences which are at least 4 AA in length and which can be recognized by any protease, for example a cysteine or an aspartate protease, are suitable for use as a protease cleavage site sequence. However, typically short sequences, i.e. of from 2 to 8 amino acids in length, can be present between the Fc domain and the linker or between the linker and the TNF ligand domain. The sequences in constituent figures 1 b to 1 j contain the amino acids ARG-SER between the Fc segment and the linker, and, in constituent FIGS. 1 c, 1 d, 1 e, 1 f, 1 g and 1 h, at least the tetrapeptide GSLQ (SEQ ID NO: 21), where appropriate extended by further amino acids C-terminally of Q, is located N-terminally of component (B). These fusion constructs which also contain a protease cleavage site, that is the fusion constructs in constituent FIGS. 1 b, 1 i and 1 j, contain the abovementioned tetrapeptide C-terminally of the protease cleavage site. The linker and the protease cleavage site are typically also separated from each other by at least two amino acids, in accordance with the figure by the dipeptide GS. The entire region between component (A) and component (B) is termed the transition region.

At the N-terminus, that is N-terminally of the Fc domain, all the fusion constructs shown in FIG. 1 b to 1 j contain a pentadecapeptide (MAIIYLILLFTAVRG) (SEQ ID NO: 22) which, in the cases depicted, corresponds to a hemagglutinin sequence. In all the cases depicted, this signal sequence is linked to the Fc segment of the fusion construct (component (A)) by way of the dipeptide LD.

The linking sequences in FIGS. 1 b to 1 j which are not framed typically correspond to restriction enzyme cleavage sites which are used to attach the individual sequence components to each other.

All the fusion constructs depicted in the constituent figures were cloned in a PCR-3 mammalian expression vector (Invitrogen).

FIG. 2 shows a Western blot photograph which depicts the purification of the fusion construct Fc:FasL according to the invention. The purified protein (5 μg/lane) was examined on 12% SDS-page under reducing (+DTT) or nonreducing (−DTT) conditions and using the fusion construct TRAILR2:Fc (that is a construct containing an immunoglobulin domain and a TNF receptor) as a control in the lanes indicated by a (+) label above the Western blot. Molecular weight markers are indicated in kDa on the left-hand side of the Western blot, while the molecular weights (110 kDa and 57 kDa, respectively), which, as expected, vary in dependence on the formation of disulfide bridges (only under nonreducing conditions) between the Fc domains, which are indicated for the fusion construct Fc:FasL according to the invention are shown by arrows on the right-hand side of the Western blot.

FIG. 3 depicts the result of the gel permeation chromatography of Fc:FasL according to the invention. For this, Fc:FasL (300 μg in 200 μl of PBS) was loaded onto a Superdex-200 column, which was equilibrated in PBS, and eluted at a rate of 0.5 ml/min. The UV profile was recorded online at 280 nm and 0.5 ml fractions were collected. The elution position is plotted below FIG. 3 and the molecular weight (in kDa), and the calibration standards, are plotted above the profile. The apparent molecular weights of the two Fc:FasL peaks were deduced from the calibration curve which is shown in the right-hand illustration in FIG. 3. The result is shown above the two peaks (850 kDa and, respectively, 440 kDa). Numbers of the investigated fractions are shown, in the order in which they were eluted, below the profile.

FIG. 4 shows electron microscopic photographs, i.e., in the order of the constituent figures, of FasL (FIG. 4 a), of ACRPΔ-FasL (FIG. 4 b), of ACRP-FasL (FIG. 4 c) and, finally, of Fc-FasL (FIG. 4 d). The individual constituent figures in each case contain different preparations of the injected amino acid sequences in alternative aspects, with a diagrammatic interpretation of the electron microscopically determined picture being depicted under each of the photographs. In this connection, the electron microscopic photographs shown in FIG. 4 a result in a dot model in the case of FasL (3 ch, that is the expected trimer of multimerizing FasL), while, in the case of ACRPΔ:FasL (FIG. 4 b), they result in a rod-shaped model having a dot end, with the dot marking the FasL component and the rod shape marking the collagen domain of ACRPΔ. FIG. 4 c results, in the case of ACRP:FasL, in a twin cherry-like structure composed of two linked rods (ACRP30 collagen domain with an attached FasL domain. Finally, the structure of Fc:FasL according to the invention is shown in FIG. 4 d, with the light dots representing FasL and the dark dots representing the Fc moiety of IgG1. The white line which links them depicts the connectivity between the different subunits.

FIG. 4 e is a depiction, in the form of a model, of the three-dimensional structure of an Fc:ligand complex according to the invention. The structure of Lymphotoxin A (PDB access number 1TNR) was selected as ligand while that of IgG 2a (PDB access number 1IGT) was selected as the Fc component.

FIG. 5 shows the specificity of the binding of Fc ligands to their respective receptors. In this case, the binding of the ligands to their receptors (in the form of receptor:COMP fusion protein) was measured using an ELISA and employing the following steps: (a) coating with murine antihuman IgG, (b) adding the respective Fc ligands at the desired concentration (as a cell supernatant), (c) adding the respective receptor-COMP fusion construct (each of which carries a tag label and was also added as a cell supernatant), (d) adding biotinylated anti-tag monoclonal antibody, (e) adding horseradish peroxidase (HRP)-coupled streptavidin, and (f) developing the assay with OPD reagent and measuring the absorbence at 490 nm.

It can be clearly seen from the diagrams shown in FIG. 5 that the fusion constructs according to the invention have strong specificity for the respective TNF receptors which are specific for the ligands (or ligand segments) which are contained in the constructs according to the invention, namely with FasL having strong specificity for Fas, Trail for Trail R2, EDAL for the EDA receptor, as expected BAFF and APRIL for the receptor BCMA, which is bifunctional in this respect, TNF for TNFR2 and CD40L for CD40R. Consequently, the preparation as a construct containing an Fc moiety has no effect on the behavior of the component (B) of a construct in regard to binding to the corresponding receptor.

FIG. 6 shows the results of binding experiments using Fc:BAFF according to the invention. As shown in FIG. 6 a, BJAB cells (BAFF-R-positive cells and HEK 293 cells (BAFF-R negative cells) were incubated with 0.05, 0.2, 0.5, 2.5, 20 or 50 μl of cell supernatants containing Fc:BAFF in a final volume of 100 microliters. Bound Fc:BAFF was identified using PE-conjugated anti-human Ig antibody and performing a FACS analysis. The result of quantifying the mean fluorescence (MFI) is shown in the right-hand diagram in FIG. 6 a. In this connection, it is clearly seen that, after the direct plots for BJAB cells and HEK 293 cells have been analyzed in the secondary plot (far right in FIG. 6 a), the mean fluorescence, as a measure of binding to the cells, increases markedly in the case of BJAB cells whereas the BAFF-R-negative HEK-293 cells do not exhibit any significantly increased mean fluorescence even when high concentrations of the Fc:BAFF according to the invention are present. Consequently, as was expected, Fc:BAFF does not bind to the BAFF-R-negative cells either, in contrast to the situation with regard to BAFF-R-positive cells.

FIG. 6 b shows the results of immunoprecipitation experiments. For these, BJAB cells (5×10⁷ per assay) were incubated for 15 minutes in 2 ml of a medium in the presence of 3 μg of Fc:FasL or of Fc:BAFF. The cells were harvested, washed in PDS, lysed in a lysis buffer (containing 1% NP-40 and immunoprecipitated using protein A Sepharose. IPs and total cell extracts were analyzed by means of the Western blotting technique using a murine anti-hBAFF-R monoclonal antibody. In this connection, it was found that the BAFF-R-positive BJAB cells bind Fc:BAFF during the incubation (right-hand lane in FIG. 6 b) and can therefore be detected with appropriate antibodies in the IP assay.

FIG. 7 shows the cytotoxicity of Fc:FasL when using serial dilutions of Fc:FasL according to the invention (as desired, the material loaded onto the column, the 850 kDa fraction or the 440 kDa fraction, as shown in FIG. 3). These serial dilutions were added to FasL-sensitive jurkat cells and were incubated at 37° C. for 16 hours. After that, the viability of the cells was examined using a PMS/MTS assay. In this connection, it was found that both the total fraction and the individual fractions have a very similar profile in regard to the ability of the cells to survive.

FIG. 8 shows the phenotypic differences between tabby mice which were treated, 10 days after birth, with Fc:EDA1 according to the invention (see FIG. 1 d) or were left untreated. WT mice served as the control (right-hand side). For this, pregnant tabby mice were injected intravenously with 400 μg of Fc:EDA1 on days 11, 13 and 15 of the pregnancy. Progeny of treated tabby mice, untreated tabby mice and wild-type mice were examined. As shown in FIG. 8 a, this examination took account of the appearance of the ear region, in particular of hair growths in the ear region. The growth of hair in treated animals corresponds to that in WT animals. The tail region in treated mice also exhibits hairiness which corresponds to that of WT mice, as well as the usual shape. The difference from untreated mice is immediately obvious.

FIG. 8 b shows histological tissue section illustrations of the retrooricular region, of the side of the body, of the tail and of the paw in paraffin using hematoxylin/eosin staining. A pronounced bald region can be seen under the ears of untreated tabby mice. With respect to this, treated tabby mice phenotypically resemble the WT. The side of the body in treated tabby mice exhibits a WT-like increase in the number of hair follicles as compared with untreated tabby mice. In the tail region, the treated mice exhibit the hair growth seen in WT mice. On the other hand, untreated tabby mice lack hair in the tail region. As is also the case in the WT, sweat glands can be seen in the tissue of the paw in treated mice (middle), as indicated by the arrows. By contrast, untreated tabby mice do not develop any sweat glands. The following features were compared:

FIG. 9 shows-a-comparison of the results which were obtained when treating tabby mice in utero with the construct according to the invention shown in FIG. 1 d with the results which were obtained in corresponding control animals.

FIG. 9 a shows a comparison of treated tabby mice (center) and untreated tabby mice (left) in adulthood (6 weeks after birth). The treatment took place as described in implementation example 4. The appearance of healthy mice, as a control, is recorded on the right. The treated animals possess a coat like that of the WT animals (including in the critical region of the tail); in the treated mice, the tail does not have any serrated appearance; the hair of treated mice exhibits the “monotrichous” hair type, which is typical for WT mice, in particular, especially long monotrichous covering hair which is entirely lacking in the untreated tabby mice.

FIG. 9 b compares the jaw and tooth structure of treated and untreated tabby mice and WT mice. The untreated tabby mice have an abnormal jaw structure and the teeth also exhibit deformities, in particular a lack of pronounced cusps. Treatment by a method according to the invention during pregnancy (treatment of the mother animal) restored the natural tooth form.

FIG. 9 c shows tissue sections of the eyelid and the cornea in untreated tabby mice, in tabby mice treated, in accordance with the invention, with Fc:EDA1, and WT control animals. The untreated tabby mice characteristically lack the Moebius glands in the eyelid. However, these glands reappear after treatment in accordance with the invention. The regeneration of the Moebius glands also prevents the keratinization of the cornea which occurs, as can clearly be seen from the tissue section shown in FIG. 9 c, in untreated tabby mice.

FIG. 9 d depicts the results of the sweat test, which results show that functional sweat glands, which are absolutely lacking in untreated tabby mice, can be observed on the paw in the case of tabby mice which have been treated in accordance with the invention. These sweat glands, which have been regained following treatment with Fc:EDA1, make it possible to demonstrate the typical physiological reactions to stimuli such as heat and stress. The sweat test itself is described in implementation example 4.

FIG. 10 shows a comparison of the results obtained following the postnatal intraperitoneal treatment of tabby mice with an Fc:EDA1 fusion construct according to the invention with the situation in untreated tabby mice and in WT control animals.

FIG. 10 a compares different body regions in the abovementioned three animal groups in regard to their phenotype. In contrast to the situation in the WT, the skin region behind the ears was not covered with hair in adult, postnatally treated animals, either. However, postnatal injection of Fc:EDA1 was able to almost completely restore tail hairiness as in the WT, on the one hand, and, on the other hand, the size of the eye aperture which is typical for the WT. The postnatal treatment according to the invention was able to virtually eliminate the “bent” tail form. In addition to this, tissue sections of the tail which were stained with hemotoxylin and eosin showed the presence of both numerous hair follicles and sebaceous glands associated with the hair follicles.

FIG. 10 b shows, microscopically and macroscopically, the phenotypes of the three groups with regard to the sweat glands on the paws. A large number of sweat glands were observed on the paws of postnatally treated adult tabby animals, with these sweat glands being indistinguishable from the WT sweat glands, as FIG. 10 b shows using tissue sections stained with hemotoxylin and eosin. These sweat glands in the treated tabby animals were found to be functional in an appropriate sweat test and reacted to physiological stimuli such as heat or stress.

In summary, therefore, it can be stated that, when treatment takes place in utero, the reversion of the phenotype which is observed following birth does not disappear in the adult animal just as the phenotypic reversions which are seen in the young animal in connection with postnatal treatment with substances according to the invention also persist in the adult animal.

The present invention is clarified by means of the following implementation examples.

IMPLEMENTATION EXAMPLES 1^(st) Implementation Example

Preparing Fc:Ligand Fusion Proteins

Preferred fusion proteins according to the invention consist of an Fc moiety derived from human immunoglobulin (component (A)), with the underlying DNA sequence not containing the immunoglobulin stop codon, and a C-terminal segment of a fragment of a ligand belonging to the TNF family (component (B)) (containing the stop codon of the underlying DNA sequence). In this connection, preferred fusion proteins according to the invention have the following structure: a signal peptide at the N terminus, then an Fc segment, for example derived from IgG, a transition region containing a linker region and a protease cleavage site, and a C-terminal segment of a member of the TNF ligand family. A diagram of a preferred fusion protein according to the invention is shown in FIG. 1 a.

In order to prepare a fusion protein according to the invention, for example a fusion protein having a preferred structure as shown in FIG. 1 a, in particular the sequences depicted in FIGS. 1 b to 1 j (SEQ ID NOS: 1-18), nucleic acid constructs were cloned into mammalian expression vectors and expressed in stable human embryonic kidney cell lines (in HEK-293 or in CHO (Chinese hamster ovary) cells). The secreted recombinant fusion proteins were isolated from the conditioned medium by means of affinity chromatography on a Protein A Sepharose column. The yields amounted to several mg per liter of the medium employed.

2^(nd) Implementation Example

Characterizing Fc:FasL Biochemically

FasL was characterized biochemically by means of SDS-PAGE analysis, with apparent molecular weight os 57 kDa and approximately 110 kDa being determined under reducing and nonreducing conditions, respectively. This demonstrated the presence of disulfide bridge-linked dimers (2 ch), as was to be expected of Fc-containing fusion proteins possessing a hinge region (see FIG. 2 as well).

A corresponding investigation carried out by means of gel permeation chromatography showed that two well defined peaks of Fc:FasL, having apparent molecular weights of approximately 440 kDa (main peak) and, respectively, approximately, 850 kDa (subsidiary peak) eluted (see FIG. 3). On the assumption that Fc:FasL has a globular form, the calculated multimer structure of FasL was 7.7 (7.7 ch) for the main species in the elution profile. However, if the protein is not typically globular in an ideal manner, this calculation is very probably based on an overestimate of the molecular weight, which means that a dimeric ligand structure (6 ch) would be perfectly possible. The form of Fc:FasL corresponding to the 440 kDa peak was examined in the electron microscope, using FasL (3 ch), oligomeric ACRP30:FasL (6+ ch) and a deletion mutant of ACRP30:FasL, namely ACRPΔ:FasL (3 ch), for comparison. FasL (3 ch) has a ball-like form (see FIG. 4 a), while ACRPΔ:FasL (3 ch) has a ball-like form with a “handle” (see FIG. 4 b) and ACRP30:FasL has the appearance of a “twin cherry”, which, as has been shown, tallies with a dimeric FasL (6 ch) structure (see FIG. 4 c).

Fc:FasL according to the invention regularly assumes a ring structure possessing 5 “balls” or an open structure possessing 5 “balls” (see FIG. 4 d). This in turn corresponds to a dimeric FasL (6 ch), with two of the balls being FasL and the remaining 3 balls being the IgG Fc components (3 polypeptide diners: 6 ch). A model representation of an Fc-ligand was developed using the known crystal structure of lymphotoxin a (a member of the TNF family) and the Fc component of IgG2a (PDB access numbers 1TNR and 1IGT), with the linker region being drawn in as a continuous line (see FIG. 4 e). This representation shows unambiguously that the ligands and the Fc moieties are of approximately similar sizes, in agreement with the observed 5-ball structure of Fc:FasL. All in all, these results indicate that the 440 kDa peak of Fc:FasL is a dimeric FasL (6 ch).

In the present disclosure, the designation “ch” stands for “chain” and thereby reflects the number of chains of the TNF ligand (for example APRIL, FasL, BAFF, EDA or Tweak) in the molecule (independently of whether a fusion construct is being considered or not). If a TNF ligand is present in trimeric form, it has three chains (3 ch), while a dimer of a ligand (for example as a result of the Fc construction according to the invention) has 6 ligand chains (6 ch).

The other fusion protein sequences according to the invention depicted in FIGS. 1 b to 1 j were characterized in an analogous manner.

3^(rd) Implementation Example

Biological activity of the Fc:ligand constructs according to the invention in vitro:

According to the invention, an ELISA-based assay was developed in order to investigate the biological properties of Fc:ligand constructs, namely their ability to bind to their corresponding receptors. In this assay, the Fc:ligand constructs were initially captured by a murine anti-human IgG monoclonal antibody. In a second step, the soluble receptors were fused to the oligomerizing domain of the cartilage oligomeric matrix protein (COMP) (see DE 19963859 and DE 10122140, the entire content of which is in each case hereby incorporated into the present disclosure), and a flag sequence was added. Receptors possessing bound ligands were identified by means of their respective flag tags (see FIG. 5). By means of using this modified ELISA assay approach, it was shown that the Fc:ligand constructs according to the invention did in fact bind to their respective native receptors, that is they do not lose their binding ability as a result of the construct structure, and the binding also takes place with a high degree of selectivity.

It was furthermore demonstrated, according to the invention, that the Fc-ligand constructs according to the invention are also able to bind to surface-expressed, endogenous receptors. It was demonstrated experimentally that, while Fc:BAFF constructs according to the invention label BAFF-R-positive BJAB cell lines in a dose-dependent manner, they do not label the BAFF-R-negative Jurkat cell line (see FIG. 6 a). In addition, it was shown that Fc:BAFF is able to specifically immunoprecipitate the endogenous BAFF receptor in BJAB cells (see FIG. 6 b).

In addition, the cytotoxicity of Fc:FasL on a FasL-sensitive Jurkat cell line was investigated. Fc:FasL was found to be highly cytotoxic on Jurkat cells, with an Ic₅₀ of 1 ng/ml (see FIG. 7) . Furthermore, it was found, in accordance with the invention, that there were no significant differences, in regard to the specific activity, between the complete preparation of Fc:FasL according to the invention and the dimeric form of Fc:FasL (6 ch) which was isolated in the 440 kDa peak and/or the oligomeric form of Fc:FasL (12 ch) which was identified in the 850 kDa peak. These results demonstrate that dimeric FasL (6 ch) is already a fully active molecule and that larger complexes do not increase the activity in this regard any further.

4^(th) Implementation Example

Biological activity of Fc:ligand constructs according to the invention in vivo:

The fusion proteins Fc:FasL and Fc:EDA were tested in vivo.

Injecting Fc:FasL into mice showed that this fusion protein exhibited cytotoxicity in vivo.

Fusion construct Fc:EDA: EDA is a member of the TNF ligand family which is physiologically responsible for the development and function, and also, in particular, for the morphogenesis, of ectodermal structures, very particularly for sweat glands, hair and teeth as epithelial structures of the ectoderm. Conversely, it is known that malfunction of EDA causes the (XL)HED syndrome in humans while, in mice, malfunction of EDA leads to what is termed the Tabby phenotype, which is essentially characterized by (i) the coat having an abnormal structure, (ii) absence of the different native hair types, (iii) loss of hair on the tail and in the region of the skin behind the ears, (iv) absence of sweat glands in the paws, (v) abnormal tooth formation and tooth eruption (vi) characteristic distortion at the tip of the tail, (vii) absence of Moebius glands (glands in the eyelid which secrete a thin film of fat for protecting the cornea from drying out; the cornea therefore becomes keratinized) and other glands, (viii) reduction in the size of the eye aperture, and (ix) lower increase in weight in young mice.

In accordance with the invention, 400 μg of Fc:EDA1 were injected in utero into female tabby mice on the 11^(th), 13^(th) and 15^(th) days of pregnancy. This fusion protein was extremely well tolerated and no contraindicating effects were observed in the treated. mice. While the Fc:EDA1 treatment did not give rise to any recognizable effects in the treated female adult mice themselves, a definite and powerful reversion of the tabby phenotype was observed in the progeny of the treated pregnant mother animals. This phenotype reversion was evident on the 10^(th) day after birth. The size of the progeny of the tabby mice which were treated during pregnancy was substantially greater than those of the control mice while their coats were smooth, black and shiny (see FIGS. 8/9). In contrast to the situation in the tabby mice, the retroauricular region in the treated tabby mice was also found to be hairy and these latter mice have normal, unbent hairy tails possessing a large number of hair follicles and the corresponding sebaceous glands, which it was possible to observe on the skin in the tail region (see FIG. 8 b).

In addition, it was possible to discern eccrine sweat glands, which were indistinguishable from the corresponding wild-type sweat glands, in tissue sections of the paws of treated, but not untreated, tabby mice (see FIG. 8 b). In the tabby mice which were treated in the embryonic stage in utero, these sweat glands were also still functional in adulthood. A sweat test was carried out for the purpose of determining the functional ability of the glands: for this, a 3.5% (w/v) solution of I₂ in ethanol was rubbed into the paws of the investigated animals and then left to dry. After that, a 50% (w/v) solution of starch in mineral oil was applied to the paws. A photograph was then taken after applying moderate heat using a hairdryer (5 s). Animals were sacrificed and tissue sections of the eyelid and the cornea stained with hemotoxylin and eosin were prepared.

The reverted phenotype was stable, as it was possible to confirm by analyzing treated tabby mice in the adult state (see FIG. 9). These mice were significantly larger than tabby mice and their coats possess, in particular, the longer, monotrichous, wild-type hair variety which is completely lacking in the tabby mice. These treated mice had no bald patches in the retroauricular region and the paws possessed eccrine sweat glands which were indistinguishable from those of the wild type. In addition to this, these sweat glands were functional (FIG. 9 a), as demonstrated in the above-described sweat test. Following treatment, the Moebius glands, which are always missing in tabby mice, were once again present and enabled normal, nonkeratinized cornea to be formed, with this providing proof of the functional competence of the Moebius glands (FIG. 9 c). The teeth of treated tabby mice were of a normal size and exhibited a wild-type pattern of tooth cusps. The third molar is small in wild-type mice and absent in tabby mice. This third molar was also missing in treated tabby mice. The results demonstrate that, when administered to pregnant mice, Fc:EDA1 according to the invention, as shown in FIG. 1 d, is able to gain access to the developing embryo, via placental Fc receptors, and to trigger induction, at EDA receptors, of the formation of native epithelial structures. In this regard, the dimerization of EDA1 (6 ch) is very probably of central importance since genetic and biochemical investigations indicate that the oligomerization of EDA is essential for its activity. It was furthermore demonstrated, in accordance with the invention, that, following the induction and establishment of epithelial structures in the developing embryo, functional EDA no longer needs to be supplied to the adult animal in order to maintain the reverted native phenotype.

5^(th) Implementation Example

In this example, an investigation was carried out to determine the extent to which a late, postnatal administration of Fc:EDA1 according to the invention was able to relieve the symptoms of the tabby phenotype in mice. Fc:EDA1 was therefore administered intraperitoneally to the young mice on the 2^(nd) (40 μg), the 4^(th) (40 μg), the 6^(th) (60 μg), the 8^(th) (100 μg) and 10^(th) (100 μg) days (or, in an alternative experimental set-up: on the 5^(th) (40 μg), on the 7^(th) (60 μg), on the 9^(th) (60 μg), on the 11^(th) and on the 13^(th) (in each case 100 μg) days after birth); a control group of tabby mice was left untreated.

The appropriately treated mice, or mice from the control group, were examined for the following phenotypic features (i) “bent” tail, (ii) formation of hair on the tail and/or behind the ear region, and (iii) eye shape. In addition, a sweat test was carried out in adult mice and tissue sections from the paw and tail skin regions of 25-day-old mice were examined.

In the case of this postnatal administration of Fc:EDA1 as well, it was possible to bring about a large number of symptoms of the tabby phenotype, in particular the restoration of the tail hair and sweat glands. It was possible to observe the tail hair on the 15^(th) day (already on the 2^(nd) day after birth) in the case of the Fc:EDA1-treated tabby mice (instead of on the 7^(th) to 9^(th) day after birth in the case of WT mice). In the case of the mice which were treated for the first time on the 5^(th) day after birth, hair formation was observed on the 18^(th) day. In the case of the treated tabby mice, the hair is initially formed on the ventral side of the tail. In all the treated tabby mice, irrespective of the time at which the treatment began, the structure and density of the tail hair did not differ from that of the tail hair in WT animals. This belated hair formation in the treated tabby mice can be readily explained by the later induction of the formation of hair follicles, as triggered by the Fc:EDA1 according to the invention which was administered. The experimental approaches described in this implementation example were unable to relieve the lack of hair (alopecia) behind the ears.

While the postnatal therapy was unable to completely revert the bent tail form, it was able to do so to a large extent. While the eye aperture of the treated tabby mice was significantly enlarged as compared with that of the untreated tabby mice, it was not precisely as large as in the WT mouse (FIG. 10 a). Functional sweat glands developed in the paws of the treated tabby mice, as was demonstrated in tissue section taken from 25-day-old treated tabby mice (FIG. 10 b). Sweat tests carried out in adult treated tabby animals demonstrated the functional ability of the sweat glands which developed in adult animals as a result of the treatment.

In summary, it can be stated that the experiments according to the invention are able to illicit an almost complete reversion of a phenotype which is to be genetically attributed to the absence of the TNF ligand EDA. The best curative successes were observed in the case of the tabby mice which were already treated with recombinant fusion protein according to the invention in utero. However, postnatal administration of fusion proteins according to the invention, e.g. Fc:EDA1, to genotypically affected animals also results in considerable curative success, i.e. in a (partial) reversion of the phenotype, in particular in the development of sweat glands (especially in the paws) and tail hair, and in an enlargement of the eye aperture. 

1. A recombinant fusion protein which contains an amino acid sequence which comprises: (a) an Fc segment of an immunoglobulin, wherein the Fc segment consists of amino acids 18 to 243 of SEQ ID NO: 6, as component (A), and (b) an extracellular moiety of EDA1, as component (B), wherein component (B) comprises amino acids 266 to 412 of SEQ ID NO:
 6. 2. The recombinant fusion protein as claimed in claim 1, wherein the recombinant fusion protein has the amino acid sequence of SEQ ID NO:
 6. 3. A composition comprising a recombinant fusion protein as claimed in claim 1 and a pharmaceutically acceptable carrier material.
 4. A DNA sequence, encoding a recombinant fusion protein as claimed in claim
 1. 5. An expression vector, wherein the expression vector contains a DNA sequence as claimed in claim
 4. 6. An isolated host cell transfected with the expression vector as claimed in claim
 5. 7. A hexamer of a recombinant fusion protein comprising six chains of the recombinant fusion protein, wherein said fusion protein comprises an amino acid sequence which comprises: (a) an Fc segment, of an immunoglobulin, wherein the Fc segment consists of amino acids 18 to 243 of SEQ ID NO: 6, as component (A), and (b) the extracellular moiety of EDA1, as component (B), wherein component (B) comprises the amino acid sequence of amino acids 266 to 412 of SEQ ID NO:
 6. 8. The hexamer of claim 7, wherein the recombinant fusion protein has the amino acid sequence of SEQ ID NO:
 6. 